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Weight, How is That Possible?

Science brain teasers require understanding of the physical or biological world and the laws that govern it.


Puzzle ID:#34428
Fun:*** (2.93)
Difficulty:*** (2.39)
Submitted By:bigSWAFF_69_Aus******
Corrected By:RomanG417




We all know that if you weigh yourself on the moon, it is less than your weight on the Earth. Can you tell me something that actually weighs more on the moon than on Earth?

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Dec 16, 2006

Yay 1st 1!

good teaser
Dec 16, 2006

Wow, that's interesting. Good teaser!
Dec 16, 2006

Except that the helium balloon would burst dut to the pressure difference.
Dec 17, 2006

I'm not sure this one's quite right. I hope I don't start anything here but...

The reason the balloon floats on Earth is because, while it does have weight (and can, in fact, be weighed, e.g. in a vacuum) that weight is less than that of the air around it (hence "lighter than air")

If it does in fact "fall" on the moon, that is because there is no atmosphere. (I think it would have to be quite close to the moon's surface for this to happen, because of the moon's weak gravitational field)

Weight is a product of mass and gravity. The mass of the balloon is constant (it is always made up of the same molecules). Gravity is lower on the moon than the Earth.

Therefore, the weight of the helium balloon is less on the moon than it is on the Earth!

(I also agree with Numpty, although I was assuming it was a "special" balloon made of some NASA style rubber that can withstand such pressure differences )
Dec 18, 2006

leftclick is correct. The Helium does in fact weigh less on the moon as well. It is just that on the moon there is no heavy atmosphere for it to float upon.
Dec 19, 2006

And, While we're being picky and scientific, it is not true that thebaloon cannot be weighed on earth. If you attach it to a spring balance, you will find out that it has negative weight, or - as the fly boys call it - "lift."
Jan 02, 2007

Our science museum weighs gases [in sealed jars] in a vacuum. Lower gravity would keep to proportions. In a dome pressurized to one atmosphere, a balloon would have its same lifting capacity, but its ascent would be slower because whole air accelerates into volume of space beneath the rising balloon under weaker gravity.
Jan 03, 2007

I voted easy and boring because it is.
Feb 28, 2007

swaff thinks hes cool.....that is all i will say you guys try to determine what I mean by thinks
Mar 06, 2007

Well I kinda liked it until I read the comments. I tend to agree that the answer is wrong and it should have been a science teaser anyway. I should have thought a bit further and realised that with a bit of physics, the mass of the molecules can be calculated and muliplied by the gravitational constant. You don't need to weigh it to determine its weight! Go Mathematics!!!
Nov 03, 2007

Not really situation more of a science one but still it was ok 7/10
Dec 23, 2007

Very clever, Keep up the good work!
Apr 30, 2008

Yup, above comments are right. At least get a teaser's answer right before you submit it.

I need some of that NASA rubber for, well, you get the idea....
Nov 03, 2010

yes and no.
clever for evryday talk but not very good for a scientist.
Oct 22, 2011

I agree that its not technically "right" but I think he means accouting for atmospheric differences between the Earth and Moon too, not just gravity. More of a trick for me but still works.
Apr 01, 2012

I believe this version is fine, and it DEFINITELY belongs in this category. Now somebody should make a version refuting this and put THAT in the science category.
Jan 13, 2013

All I can say is "Ho Hum!" (
Jan 13, 2013

I'll check it out on my next trip to the moon. And to GW
Jan 13, 2013

Didn't get it, but I'm not a science kinda gal. Lots of information in the comments that I didn't know.
Jan 13, 2013

If, as unclemyke says, the balloon has a negative weight on Earth, but a positive weight on the Moon due to the lack of atmosphere, then surely it does, in fact, weigh more on the Moon than on Earth?
Jan 14, 2013

@spikethru4 - The balloon on earth doesn't really have negative weight. It's just that the buoyancy of the balloon gives it the appearance of negative weight. You still weigh the same either on land or in the water, but your buoyancy in water gives the impression that you weigh less. If you measure the weight of a balloon in a vacuum chamber (this removes any buoyancy effect and the balloon will not float) both on earth and on the moon, the weight will be significantly less on the moon.
Jan 15, 2013

Thanks, @elentir, that's a good explanation. I wasn't altogether comfortable with the concept of 'negative weight', since the mass must be positive and the gravitational force is positive, therefore weight must also be always positive. It's clear now that the air resistance is a separate force that counteracts the weight, giving a resultant force in the opposite direction (i.e. upwards).
Sep 25, 2013

So according to that reasoning, a ping pong ball floating on water has no weight either, until you take it out of the water? Being buoyed within/on top of a mass of a substance less dense than itself does not negate the fact that an object has weight.
Sep 25, 2013

Not at all. The ping pong ball's weight is only one force acting on it. The buoyancy of the water is another force. If the ball is resting on top of the water, then the two forces are equal and opposite.

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